Oops! I have to fix that schematic... Yes, my cathodes are grounded properly (although I guess I'd better check when I get home?). I'll take a look at your schematic and try midpull resistors some more.
On Feb 9, 1:25 am, threeneurons <[email protected]> wrote: > On Feb 8, 9:10 pm, will <[email protected]> wrote: > > > This is so confusing! My DMM measures literally 10mV across its > > internal 10megohm shunt from (off) anode to ground, which means that > > the anode is truly OFF... My DMM reports infinite resistance from > > cathode to ground when it's set to off... Everything seems to be > > working perfectly! > > > As a possibly related side note, one of the tubes is slightly brighter > > than the other, even though their sustaining voltages are within a > > quarter of a volt of each other and their anode resistors are within > > 500 ohms. Could this mean anything? > > http://sites.google.com/site/willyager/nixie-clock > > Not to ask a dumb question, but are the emitters of your cathode > transistors grounded ? The schematic omits showing that connection. > Since the board is hand wired, you probably have grounded them, > indifferent to the schematic omission. If you did leave them > unconnected, the problem would be worse. > > I'm still thinking its one of the two issues already mentioned: (1) > Timing and/or (2) leakage. > > The 'midpull' resistors, mentioned, usually can address the leakage > problem. I think they showed only connections to the cathodes, but the > anodes should also have a resistor tied to them (100K-470K) that's > connected to a middle voltage (80V-100V). > > My third nixie clock uses 4 IN-14s, is multiplexed (1 of 4), by a AVR > mega8 uC: > > http://snipurl.com/10zg1u > > The cathode driver is a pair of SN75468 HV darlington pairs. Part of > one chip is used as part of the anode drive. The coupling caps are > needed since the SN75468 can only handle 100V, but the MPSA92s are all > the way up at ~200V. Cap coupling was (and is) and old technique to do > level shifting. It has midpulls on both the cathode and anode side. No > ghosting at all. Been running since 2004. -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB.
